Propellant gas operation/initiation of a non-pyrotechnic projectile tracer

ABSTRACT

The present disclosure is directed to propellant gas initiation of a non-pyrotechnic projectile tracer. In some embodiments, cartridge-propellant gasses act upon a piston to break a frangible chemiluminescent liquid chemical ampoule to initiate a luminous reaction independently of and prior to any projectile motion. The piston may be a distinct piston, a separate component functioning as a piston, or the overall tracer container acting in the manner of a piston. Embodiments of the disclosure are applicable to direct-fire ammunition ranging from small arms through large caliber main battle tank ammunition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/474,582, filed Apr. 12, 2011 and titled PROPELLANT GAS OPERATION/INITIATION OF A NON-PYROTECHNIC PROJECTILE TRACER, which is incorporated in its entirety herein by reference thereto.

TECHNICAL FIELD

The present invention is related to projectile tracer assemblies, and more particularly to non-pyrotechnic projectile tracer assemblies and related methods.

BACKGROUND

Base-mounted tracers for gun-launched projectiles have traditionally been characterized by the use of pyrotechnic compounds that are ignited/initiated by the act of firing the projectile. The hot propellant gases come into contact with and ignite the tracer's pyrotechnic compounds. Upon the projectile's exit from the launching gun and for a portion of or all of the projectile's flight, the tracer marks the projectile's trajectory by virtue of the combusting pyrotechnic tracer compound.

Because tracers are pyrotechnic in nature, they present a potential fire hazard during employment, particularly on firing ranges during training operations. This issue is addressed by the use of non-pyrotechnic tracer elements such as liquid bi-chemical chemiluminescent elements (U.S. Pat. No. 6,990,905). Typically, chemiluminescent systems consist of two liquid chemicals that when brought together in intimate contact experience a reaction, the products of which are visible light and infrared energy. Initially, the two chemicals are kept separate by the use of special/frangible containers (transparent or equipped with a transparent section) positioned coaxially one inside the other. Upon activation, one or both of these special/frangible containers is ruptured, thus allowing the two liquid chemicals to come into contact with each other and start the reaction. The rupturing of the container(s) is accomplished by subjecting the projectile to stimulation at the desired time of tracer activation, typically launch and/or target impact. Launch stimuli may be predicated upon acceleration (setback) of the projectile, spin-up of spin-stabilized projectiles in guns that are rifled, and deceleration (set forward) of the projectile as it emerges from the gun's barrel (ending acceleration) and encounters open air. These stimuli act upon designed mechanisms, such as inertia masses (US Patent Application Publication No. 2010/0175577), to rupture the container(s).

SUMMARY

The present invention overcomes drawbacks experienced in the prior art and provides other benefits. Embodiments of the invention provide a non-pyrotechnic projectile tracer, such as an ammunition round with chemiluminescent tracer portion configured for propellant gas operation or initiation of the non-pyrotechnic tracer material upon firing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of a projectile having a tracer configured in accordance with embodiments of the disclosure.

FIG. 2 is a cross-sectional side view of a projectile having a tracer with a piston-activator configured in accordance with embodiments of the disclosure.

FIG. 3 is a cross-sectional side view of a small-caliber projectile having a tracer configured in accordance with embodiments of the disclosure.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional side view of a projectile 100 having a tracer 110 configured in accordance with embodiments of the disclosure. The tracer 110 includes an outer cylindrical ampoule 112 positioned within a tracer cavity 114. In one embodiment, the outer ampoule 112 is non-frangible when the projectile is fired from a gun or other launching mechanism. The illustrated outer ampoule 112 has an open internally-threaded end 116 and an opposite closed end 118 with a pronounced protrusion 120. The outer ampoule 112 is positioned on an aft end 122 of the projectile 100 such that the protrusion 120 on the outer ampoule 112 is bearing against a blind end 124 of the projectile tracer cavity 114. The tracer 110 includes an externally threaded stepped closure 126 equipped with a central window 128 constructed of a rugged, high temperature resistant material, such as sapphire. The window 128 can be substantially transparent to visible and/or infrared radiation. The stepped closure 126 can have threads to match the outer ampoule 112. The tracer 110 further includes an inner frangible cylindrical ampoule 130 positioned longitudinally within the outer ampoule 112, the inner ampoule 130 having a first end 132 bearing against the outer ampoule protrusion 120 and a second end 134 opposite the first end 132 and proximate to the central window 128. The outer ampoule 112 can contain a first chemiluminescent component and the inner ampoule 130 can contain a second chemiluminescent component.

The tracer 110 can further include an externally threaded capture ring 136 (threaded to match the designated projectile interface) whose central hole can permit a smooth sliding fit with the stepped closure 126. The capture ring 136 can include an internal sliding seal that bears upon the smaller diameter section of the stepped closure 126. The entire outer ampoule 112 is sized to be a sliding fit in the projectile's tracer cavity 114. The tracer 110 is secured in the projectile 100 by the capture ring 136 external threads mating up with the projectile tracer cavity 114 internal threads. When assembled, the outer ampoule 112 is captured in the projectile tracer cavity 114 by the capture ring 136 with the outer ampoule protrusion 120 bearing against the blind closed end 124 of the projectile tracer cavity 114 and the transparent window 128 exposed and flush with the aft end of the capture ring 136. In some embodiments, the projectile 100 comprises a medium (i.e., 20-75 mm) or large caliber (75 mm and larger) direct fire ammunition.

The tracer 110 activation sequence is as follows: upon firing, the cartridge primer ignites the main propelling charge which generates the propelling gasses. As the cartridge internal pressure rapidly increases, the cartridge internal pressure bears against all exposed surfaces (the cartridge case internal surfaces and the projectile 100 base) including the smaller diameter section of the stepped tracer closure 126 with the tracer transparent window 128. The propelling gas pressure force generated on the stepped tracer closure column 126 loads the tracer outer ampoule 112, which in turn passes the column load against the closed end protrusion 120 that in turn bears against the blind end 124 of the projectile tracer cavity 114. At a predetermined pressure value, the protrusion 120 is loaded to the point where it collapses, crushing the frangible inner ampoule 130. This action frees the two liquid chemiluminescent chemicals to come into contact and react in a luminescent reaction, while maintaining a liquid-tight integrity. The radiation released from this reaction (visible and/or infrared) escapes from the outer ampoule 112 through the transparent window 128 facing aft towards the gunner. The forward sliding motion of the outer ampoule 112 is arrested when the outer ampoule 112 is crushed to the point where the two liquid chemicals are hydraulically compressed, halting the forward motion of the outer ampoule 112. In some embodiments, a physical/mechanical motion limiting/stop feature (not illustrated) can also be utilized. The tracer 110 is accordingly activated independent of the motion of the projectile 100, (including projectile acceleration/setback, spin-up, and deceleration/set-forward/impact).

FIG. 2 is a cross-sectional side view of a projectile 200 having a tracer 210 with a piston-activator 240 configured in accordance with embodiments of the disclosure. The projectile 200 includes several features generally similar to those described with reference to FIG. 1, including an inner ampoule 230 positioned within an outer ampoule 212 within a projectile tracer cavity 214. The inner ampoule 230 is positioned against an outer ampoule protrusion 220 as described above with reference to FIG. 1. In this embodiment, the tracer 210 is shielded from the propellant gasses by a stepped piston 240, the smaller diameter of which bears against an aft surface 242 of the outer ampoule 212, leaving the larger diameter's aft end 244 to be acted upon by the propellant gasses. The whole piston 240 is supported by the projectile's aft end or drag cone/fin 252. A plurality of small equalizing ports/holes 246 is positioned in a tapered forward-facing end 248 of a projectile drag cone/fin 252 that communicates with the stepped diameter of the piston 240. The piston 240 is held in position by a plurality of shear pins 250 arranged radially around the periphery of the piston's larger diameter and anchored in the projectile aft end or drag cone/fin 252. The sheer pins 250 are configured to securely maintain the piston's position and prevent activation of the tracer 210 prior to firing of the projectile, such as during rough handling and/or transport. The shear pins 250, however, are configured so they will shear and release the piston upon application of very high loads applied on the piston by the pressurized gas generated upon firing of the projectile.

The piston 240 is positioned in the projectile's aft end or drag cone/fin 252 such that the force of the propellant gasses can push the piston 240 forward a calculated distance after first shearing the shear pins 250. In some operational settings, the propellant gasses provide approximately 82,000 pounds psi of force at launch. The moving piston 240 transmits this force to the tracer ampoule 212 causing it to move forward as well. This forward motion crushes the outer ampoule protrusion 220 and initiates the tracer action in a manner similar to the embodiment described above with reference to FIG. 1. Upon shot exit from the gun barrel and after the projectile 200 transitions the muzzle shock bottle phenomenon, the forward motion of the projectile 200 causes a near vacuum/low-pressure area to be established at the projectile's aft end or drag cone/fin 252 as well as air to be forced into the forward facing equalizing ports 246. This near vacuum/low pressure acting upon the aft face of the large diameter section of the piston 240, coupled with air pressure on the forward surface of the stepped section of the piston 240 from the air entering the forward facing equalizing ports 246, results in a force to effect the separation of the piston 240 from the projectile 200. This separation unmasks the functioning tracer 210.

FIG. 3 is a cross-sectional side view of a small-caliber projectile 300 having a tracer 310 configured in accordance with embodiments of the disclosure. The projectile 300 includes several features generally similar to those described above with reference to FIGS. 1 and 2. In this embodiment, the projectile 300 has a tubular aft end 344 in which is positioned a metallic cylindrical liner 360. In some embodiments, the liner 360 can be steel or an alloy of steel. The liner 360 serves as a re-enforcing element to maintain projectile integrity upon the spin-stabilized projectile's 300 exit from the barrel as centrifugal forces act upon the chemiluminescent payload to burst the projectile 300. A frangible inner ampoule 330 containing one of the chemiluminescent components is positioned within the liner 360. The frangible ampoule 330 has a smaller diameter than the inside diameter of the metallic liner 360 and its forward end 362 is nested into a centrally-located depression 364. In some embodiments, the inner ampoule 330 is long enough so that when seated into the projectile 300, an aft end 366 projects slightly from an aft end 368 of the metallic liner 360; i.e., the inner ampoule 330 is slightly longer than the metallic liner 360. An annular space 370 between the frangible ampoule 330 and the inside diameter of the metallic liner 360 is nearly filled with the second chemiluminescent component leaving a small air space. A transparent lens 328 manufactured from a tough heat and shock resistant transparent material (such as, for example, artificial sapphire as commonly used with scratch-proof watch crystals), is treated with a sealant on its periphery then positioned in the base of the projectile 300, in effect sealing the aft open end 344 of the projectile 300. The lens 328 is held in this position by the sealant as well as a cannelure/crimp groove 372 impressed on the projectile's outer surface 374. The cannelure 372 is configured to maintain the lens' 328 position and prevent activation of the tracer 310 during handling and transport. Lastly, the lens 328 is secured by rolling the aft open end 344 of the projectile copper jacket 374 over the aft outer edge of the lens 328. In some embodiments, the projectile 300 is a small-caliber ammunition, such as 5.56 mm×45 (.22-caliber), 7.62 mm×51 (.30-caliber), 12.7 mm×99 (.50 caliber Browning Machine Gun), and up to 20 mm caliber.

The tracer 310 functions at firing by the lens 328 being moved forward by the propelling gas pressure acting upon it. During this slight forward motion, independent of the projectile 300, the lens 328 first overcomes the cannelure 372 then fractures the internal frangible ampoule 330, allowing the chemiluminescent components to mix and fluoresce. In some embodiments, the lens 328 can make contact with the aft end 368 of the metallic liner 360 shortly before the lens 328 comes into light contact with the aft end 366 of the frangible ampoule 330. The small air space in the annular chemiluminescent component 370 enables the slight forward motion of the lens 328 without the hydraulic resistance should the chemiluminescent components become solidly compressed. The lens' 328 forward motion is halted by the lens 328 outer periphery encountering the annular aft end 368 of the metallic liner 360. The radiation liberated by the chemiluminescent payload escapes rearward from the projectile 300 through the transparent lens 328 to be seen by the weapon's gunner/spotter.

From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

1. A projectile having a chemiluminescent tracer and being fireable from a launching mechanism, comprising: a tracer having a tracer cavity and a threaded stepped closure with a central window substantially transparent to visible and/or infrared radiation, the stepped closure having first threads; an outer ampoule positioned within the tracer cavity, the ampoule containing a first chemiluminescent component and being non-frangible when the projectile is fired from a launching mechanism, the outer ampoule has an open end and a closed end opposite the open end, the closed end having a pronounced protrusion, the outer ampoule is positioned on an aft end of the projectile such that the protrusion is bearing against a blind end of the projectile tracer cavity; a frangible cylindrical inner ampoule positioned longitudinally within the outer ampoule, the inner ampoule containing a second chemiluminescent component and having a first end bearing against the outer ampoule protrusion and a second end opposite the first end and proximate to the central window; an externally threaded capture ring having a central hole that permits a smooth sliding fit with the stepped closure, the capture ring having a internal sliding seal that bears upon a smaller diameter section of the stepped closure, and wherein the entire outer ampoule is sized to be a sliding fit in the projectile's tracer cavity, the tracer having external second threads that mate with the first threads of the stepped closure; wherein the outer ampoule protrusion bears against the blind closed end of the projectile tracer cavity and the transparent window is exposed and flush with the aft end of the capture ring such that chemiluminescent light generated upon mixing of the first and second chemiluminescent components after the inner ampoule breaks can be seen through the transparent window.
 2. A projectile having a chemiluminescent tracer, comprising: a tracer having a tracer cavity and a closure with a central window; a first ampoule in the tracer cavity and containing a first chemiluminescent component, the first ampoule being configured to remain in tact when the projectile is fired from a launching mechanism, the first ampoule having a closed end opposite with a protrusion bearing against the tracer cavity; a frangible second ampoule positioned longitudinally within the first ampoule, the second ampoule containing a second chemiluminescent component that will generate light when mixed with the first chemiluminescent component, the second ampoule having a first end bearing against the protrusion and a second end opposite the first end and proximate to the central window; a capture ring having an internal sliding seal that bears upon a smaller diameter section of the stepped closure, and wherein the entire outer ampoule is sized to be a sliding fit in the tracer cavity; wherein the transparent window is exposed and flush with the aft end of the capture ring such that the chemiluminescent light generated upon mixing of the first and second chemiluminescent components after the second ampoule breaks can be seen through the transparent window. 